Japanese Unexamined Patent Application Publication No. JP 60-127327 Y (Patent document 1) discloses a folding hat in which an outer circumferential edge of a brim is provided with a hollow ring part (space part), a ring made of endless elastomeric thin wire, such as stainless steel being charged thereinto as a core. According to this document 1, when the hat is unfolded, the brim expands toward outside in a radial direction with the elasticity of the ring, so that the hat can be used as a sun visor and a rain visor, and, when the hat is not in use, three overlapped circles are formed by overlapping the brim on the inside by bringing right and left sides of the brim to twist it in the shape of a figure 8, so that the hat can be folded in a circle shape having one-third of a size at use. If a part of the circles is pulled outside or the like, the hat can be instantly restored from the folded state to the developed state (use state) by the elasticity of the ring.
The hat of Patent document 1 has the brim comprised of an extremely flexible material so as to easily fold up. In contrast, the ring made of elastomeric thin wire has a vertically long rectangular cross-section and angular edges. Therefore, in the case of the hat of Patent document 1, there is a greater risk that friction with the edges of the ring may cause damage to the hollow part of the brim outer periphery through repeated folding and unfolding. Because constant tension is always applied to the space part by the elasticity of the ring, a damaged slit may easily become large immediately when the cloth is torn a little. Particularly, if the ring is made of stainless steel and thin, the edges become sharp like a knife, so the cloth is easily damaged and there is the risk of wounding the user.
The present invention has been made to solve the above-mentioned problems and aims to provide a folding hat which eliminates the risk of damaging the cloth by an elastic ring and which can be safely used for a long period of time.